Structure and dynamics in dense suspensions of micellar nanocolloids

We present an experimental description of the dynamics of a dense colloidal suspension of model hairy nanoparticles using dynamic light scattering. Th ese colloids were obtained by cross-linking the poly(2-cinnamoylethyl metha crylate) cores of polystyrene-block-poly(2-cinnamoylethyl methacrylate), co polymer micelles. Because of their small size and the small spacing of thei r liquidlike structure, as detected with small-angle neutron scattering, th ese particles enable the systematic investigation of the low-scattering wav evector (q) fraction of the dynamic structure factor (S(q,t)) away from the peak, which relates to the osmotic modulus of the suspension. The two rela xation processes contributing to S(q,t) are the fast cooperative diffusion of the concentration fluctuations (hair interactions) and the self-diffusio n of the slightly polydisperse cores (incoherent contribution). The former speeds up and loses intensity with increasing concentration, analogous to l inear and hyperstar polymer solutions, whereas the latter slows down and ex hibits virtually increasing intensity with concentration as a consequence o f the correlation hole at low q's, much like the hard sphere colloids. The study of these hairy particles contributes to the overall picture of the dy namic response of concentrated colloidal suspensions sterically stabilized by grafted macromolecules.